Harper is one of the best young players we have ever seen, and his habit of going all out all the time is why he’s fun to watch -- and why the Nationals should be concerned, and probably already are.

If you read accounts of baseball from the last years just before World War II, the young players who were the Harper and Mike Trout of their time were Ted Williams and a Dodgers outfielder named Pete Reiser. Williams is in the discussion as the greatest hitter of all time; Reiser is mostly unknown to history, other than as a cautionary tale.

Reiser played in 58 games in his first season with the Brooklyn Dodgers in 1940 at age 21, and the next summer, he won the National League batting title, hitting .343 with 70 extra-base hits; he led the NL in runs scored with 117, and he finished second in the MVP voting. Leo Durocher was Reiser’s first manager and, years later, was the first manager for Willie Mays. Durocher would speak of them, in so many words, as equals in their talent. "Mays had everything,” Durocher said. “Pete Reiser had everything but luck."

But much of Reiser’s luck was self-inflicted, because he had a tendency to run into outfield walls, in a seeming attempt to run through them in pursuit of the baseball. (He once fractured his skull running into the wall.) This was an admirable trait in some respects, because his effort was always at a maximum level. At the same time, the crazed pursuit of excellence essentially wrecked his career.

Mays didn’t run into fences in the way that Reiser did, nor did Williams or Joe DiMaggio. They’re all in the Hall of Fame. Reiser is not.

Earlier this year, Nationals manager Davey Johnson talked about the need for Harper to take down his intensity a notch or two, and the type of play we saw in Monday’s game is exactly what Johnson is talking about. It’s one thing to go full speed on every ground ball, to go first to third with all the zeal of a strong safety rushing to blast the running back coming through the hole. But it’s another thing to attack every play, regardless of the situation and the place on the field, as though making that catch is pivotal. Because not every play and situation is the same, and is worthy of reckless effort. At the moment that Harper barreled into the wall, the Nationals had a 6-0 lead in the fifth inning, with the game under complete control.